Recall…

1. Recall… • Evolution is change over time • Proof of evolution • Fossils • Comparative anatomy • Embryology • Cytology • Biochemistry • The sequence of amino acids in the cytochrome c molecule, an enzyme found in mitochondria, is identical in humans and chimpanzees fossils

2. Early Earth • Composition: molten body  solid crust surface (hot) • Atmosphere – probably gases from volcanic eruptions • Oxygen-poor • Eventual cooling, formation of oceans  life on Earth (~3.5 billion yrs ago)

3. The Early Earth “soup” Heterotrophic Hypothesis: organic chemistry may spontaneously form from inorganic chemistry • autotrophs developed after the evolution of heterotrophs partly because the primitive environment of the Earth lacked carbon dioxide • Miller-Urey Experiment

4. Origin of Life: Cells Prokaryotes have no nucleus and no membrane bound organelles • First cells: prokaryotic • Small • Capable of living in extreme environments (like deep sea vents) • Then the appearance of photosynthesizing prokaryotes (cyanobacteria) • Production of oxygen  ozone layer  appearance of eukaryotes

5. Appearance of Eukaryotes • ~1.8 billion years ago • Endosymbiont Theory: eukaryotic cell ancestors living in association with prokaryotic cells • Evidence for the endosymbiont theory • mtDNA & cpDNA, and its circular arrangement • Prokaryotic ribosomes • Mitochondria and chloroplast reproduction by fission Eukaroytes have a nucleus and membrane bound organelles

6. Theories of Evolution • Lamarck- use and disuse • When environments changed, organisms had to change their behavior to survive. • If they began to use an organ more than they had in the past, it would increase in its lifetime. • If a giraffe stretched its neck for leaves, for example, a "nervous fluid" would flow into its neck and make it longer. • Its offspring would inherit the longer neck, and continued stretching would make it longer still over several generations. • Meanwhile organs that organisms stopped using would shrink.

7. Darwin- natural selection • Finches • Peppered moth game • peppered moth simulation • Ant simulation

8. Natural Selection • Conditions vital to this process are • Overproduction • Finite resources • Genetic variation (mutation and sexual reproduction including crossing over) • Adaptive value • Selection by the environment of those better able to survive and reproduce • “survival of fittest”

9. Natural selection acting on phenotypes • Stabilizing selection: favors a mean, eliminates extremes (ex: birth weight) • Directional selection: favors one extreme (ex: peppered moth) • Disruptive selection: favors two extremes, eliminates the mean (ex: Northern water snakes color patterns)

10. Examples of Adaptation • Camouflage: Cuttlefish, Leafy Sea Dragon

11. Examples of Adaptation • Mimicry: evolving to resemble another species (drone fly, ash borer)

13. Gradualism vs. punctuated equilibrium • Gradualism: selection and variation that happens more gradually • Over a short period of time it is hard to notice • Punctuated equilibrium: change comes in spurts • There is a period of very little change, and then one or a few huge changes occur